1. Field of the Invention
The present invention relates to a printing device that performs printing according to print image data transmitted from an upper level device and a method of controlling a printing device.
2. Description of the Related Art
As an image forming system, a system has been known which includes an image forming apparatus and a DFE (Digital Front End Processor) server that is an upper level device for sending print data to the image forming apparatus and instructing the image forming apparatus to perform printing. There is also a known system in which a DFE server provided with a drawing function generates a raster image by using a raster image processor (RIP), on the basis of print data written in PDL (Page Description Language) that is transmitted from an upper level device, and transfers the generated raster image to an image forming apparatus (see, for example, Japanese Patent Application Laid-open No. 2004-287519).
Different from the image forming apparatus described above, a printer device provided with a printer controller, a printer engine, and data lines to connect the printer controller to the printer engine is known (see, for example, Japanese Patent Application Laid-open No. 2002-254763). In the printer device, a control line used for exchanging various types of control information is separate from the data lines used for exchanging print data, in order to realize a high-speed data transfer.
In Japanese Patent Application Laid-open No. 2002-254763, the configuration is disclosed in which the control line and the data lines between the printer controller and the printer engine are separate from each other in order to increase a printing speed of the printer device as a whole. Furthermore, the data lines between the printer controller and the printer engine are separate for each color. Therefore, it is possible to transfer pieces of print data of respective color components in parallel, enabling to realize the high-speed data transfer.
If the configuration as disclosed in Japanese Patent Application Laid-open No. 2002-254763, in which the control line is separate from the data lines and the data lines are separate for each color, is applied to the image forming system as disclosed in Japanese Patent Application Laid-open No. 2004-287519, it may be possible to realize a high-speed data transfer between the DFE server and the image forming apparatus.
However, in the image forming system with the above configuration, if a failure occurs in a control unit (a data transfer control unit) that controls data transfer, it becomes impossible to transfer data to an output unit (for example, a head) on the downstream side of the data transfer control unit. Therefore, it is needed to suspend the operation of the image forming system and cope with the failure of the data transfer control unit (for example, replace the data transfer control unit when the failure is due to a hardware problem or re-install software when the failure is due to a software problem). That is, there is a problem in that there is no effective method of coping with the failure of the data transfer control unit but to interrupt the operation of the image forming system.